Database
db={"users":[{_id:ObjectId("58ebf8f24d52e9ab59b5538b"),store_ids:[ObjectId("58dd4bb10e2898b0057be648"),ObjectId("58ecd57d1a2f48e408ea2a30"),ObjectId("58e7a0766de7403f5118afea"),]}],"stores":[{_id:ObjectId("58dd4bb10e2898b0057be648"),name:"Store A",},{_id:ObjectId("58ecd57d1a2f48e408ea2a30"),name:"Store B",},{_id:ObjectId("58e7a0766de7403f5118afea"),name:"Store C"}]}
Query
db.users.aggregate([{"$lookup":{"from":"stores","localField":"store_ids","foreignField":"_id","as":"stores"}},{$project:{store_ids:0}}])